1. Field of the Invention
This invention relates to a manually operated safety device having utility in a system for igniting a pyrotechnic device such as a flare launched from an aircraft and suspended by a parachute.
2. Description of the Prior Art
Many pyrotechnic devices such as military flares and rockets utilize the pulling of a lanyard to release a firing pin to effect ignition or to perform other functions that must be executed after the pyrotechnic device clears a launcher or other hardware. A safety hazard exists with pyrotechnic devices of this type in that if a flare, for example, is dropped during handling or the lanyard inadvertently is caused to be pulled and the primer to be fired, a very serious accident can result.
In the prior art a number of proposals have been advanced for solving this problem. The patents discussed below are a representative sample of a number of these proposals.
An ignition system for air dropped illuminating flares triggered by the parachute shock pull on the ignition lanyard is disclosed in U.S. Pat. No. 3,736,877 granted on June 5, 1973. The ignition propellant is housed in plastic foam for protection and for absorbing the impact shock if the flare should inadvertently be dropped.
A SAFE-ARM device for solid propellant rocket motors is disclosed in U.S. Pat. No. 3,529,418 granted Sept. 22, 1970. In this device there is provided a manually movable plug that in one position precludes accidental or inadvertent ignition of the motor, and in another position permits ignition of the motor on command. When in the safe position, the plug disperses to the atmosphere any gases or flame that result from accidental or inadvertent ignition, with spring tension means maintaining the plug in the safe position.
A similar SAFE-ARM device for solid propellant rocket motors is disclosed in U.S. Pat. No. 3,423,931 wherein the movable plug comprises a double ended piston that is movable in a tubular body and functions as a seal at either end of the body, with the toggle action of a spring maintaining the piston in the safe position.
U.S. Pat. No. 2,392,884 granted Jan. 15, 1946 discloses a fuze for projectiles having safe and arm positions. There is included within the fuze body an unbalanced cylindrical detonator block which normally is held in a fixed safe position by a shear pin. Upon firing of the projectile, setback shears the shear pin and centrifugal force resulting from projectile rotation turns the unbalanced block to the armed position. In the armed position, a passage in the block allows flame and hot gas resulting from the impact of a firing pin and primer to communicate with a booster charge and thereby transmit detonation to a burster charge that fills the main body of the projectile. In the safe position, such communication is precluded by the unbalanced block.
While the foregoing prior art patents recognize some of the desirable attributes of a flare manual safety device, there remain problems with respect to locking the device in the safe position and maintaining it in that position in the event the primer is accidentally or inadvertently fired during handling, and with respect to preventing the gases, in such event, from venting to the outside of the flare. There remain problems also with respect to preventing inadvertent arming or safing of the flare due to shock or vibration and in sealing the flare against moisture and other undesirable foreign matter.